Electrical Practice

For a grounded electrical system supplied by a feeder or branch circuit, the equipment grounding conductor shall be sized in accordance with ___________.

• the ungrounded circuit conductors

• the overcurrent protective device

• the service entrance conductors

• the grounding electrode

Answer explanation

The equipment grounding conductor must be sized according to the overcurrent protective device to ensure it can safely carry fault currents without overheating, providing effective protection for the electrical system.

In movie theaters, all switches for controlling the emergency lighting systems shall be located ______

• on the stage

• in the lobby

• in the managers office

• in the projection booth

Answer explanation

In movie theaters, emergency lighting system switches must be easily accessible for safety. Placing them in the lobby ensures quick access for staff during emergencies, making 'in the lobby' the correct choice.

When connecting utilization equipment to a 20-ampere rated branch-circuit that also serves luminaires , the utilization equipment shall have an ampere rating not more than _______.

• 10 amperes

• 15 amperes

• 16 amperes

• 12 amperes

Answer explanation

When connecting utilization equipment to a 20-ampere branch circuit with luminaires, the equipment's ampere rating must not exceed 10 amperes to ensure safe operation and prevent overload, making 10 amperes the correct choice.

Where there are tenant spaces in a retail shopping mall, each occupant shall have access to the main disconnecting means, EXCEPT:

• where the service and maintenance are provided by the building management

• where there are more than six disconnecting means

• where the primary feeder transformer does not exceed 600 volts

• where the secondary of the service transformer does not exceed 240 volts to ground

Answer explanation

The correct choice is where the service and maintenance are provided by the building management, as this allows the management to control access to the main disconnecting means, ensuring safety and efficiency.

For lighting systems operating at 30-volts or less, the output circuits of the power supply are to be rated not more than ________.

• 15 amperes

• 20 amperes

• 25 amperes

• 30 amperes

Answer explanation

For lighting systems at 30-volts or less, the output circuits must not exceed 25 amperes to ensure safety and compliance with electrical standards. Therefore, the correct answer is 25 amperes.

Where a service riser is installed in a wet location and contains THWN insulated conductors, the wiring method used is ___________

• is permitted to be type AC cable

• shall be rigid metal conduit

• is permitted to be electrical metallic tubing

• shall be liquid-tight flexible metal conduit

Answer explanation

In wet locations, THWN insulated conductors can be installed using electrical metallic tubing (EMT), which provides adequate protection against moisture. Other options may not meet the necessary requirements for wet environments.

Where a 90 ampere, 240-Volt, single phase load is located 225 feet from a panelboard and is supplied with a size 3 awg copper conductors, determine the approximate voltage drop of the conductors.

VD = 2KID / CM K= 12.9

• 6 V

• 4 V

• 8 V

• 10 V

Answer explanation

Using the formula VD = 2KID / CM, where K = 12.9, I = 90 A, D = 450 ft (225 ft each way), and CM for 3 AWG copper is 83.5, we calculate VD to be approximately 10 V, making 10 V the correct answer.

Determine the MAXIMUM number of 125-volt, general purpose duplex receptacles permitted to be protected by a 20-ampere, 120-volt single pole circuit in a commercial building

Volts x amperes - then - total va / va of one receptacle

• 18

• 15

• 13

• 10

Answer explanation

To find the maximum number of receptacles, calculate 20A x 120V = 2400VA. Each receptacle is rated at 180VA (2 x 15A). Thus, 2400VA / 180VA = 13.33, rounded down to 13. Therefore, the maximum is 13 receptacles.

In a commercial building, the minimum size of the equipment grounding conductor for a 100-ampere circuit shall be ___________.

• 8 AWG

• 10 AWG

• 6 AWG

• 4 AWG

Answer explanation

The minimum size of the equipment grounding conductor for a 100-ampere circuit is 8 AWG, as specified in the National Electrical Code (NEC). This ensures adequate grounding for safety and compliance.

When installing a 3-phase, 4-wire system, the neutral conductor shall be sized based on ___________.

• the largest ungrounded conductor

• the smallest ungrounded conductor

• the total load

• the overcurrent protection device

Answer explanation

The neutral conductor in a 3-phase, 4-wire system must be sized based on the total load to ensure it can safely carry the return current from all phases, preventing overheating and ensuring system stability.